A comprehensive review on the effect of ethers, antioxidants, and cetane improver additives on biodiesel-diesel blend in CI engine performance and emission characteristics

Due to the energy security and environmental pollution from engines working with conventional fuels, various experimental research has been carried out to find alternative, environmentally friendly, renewable, and sustainable fuels. Biodiesel is an eco-friendly and alternative biofuel fuel that can substitute partially or fully diesel fuel for a compression ignition engine. This paper provides a comprehensive review of the performance, emission, and combustion characteristics of the diesel-biodiesel blend on diesel engines using ether, antioxidant, and cetane improver additives. The energy and exergy performance of biodiesel on a diesel engine is also discussed. The general impression is that ether especially DEE is the promising one that has a significant effect on improving the physical properties of the biodiesel, increasing the performance, and reducing the exhaust emission characteristics. Antioxidants are also important additives for biodiesel to improve the oxidation stability and reduce the NOx emission significantly but increase the CO and HC emissions. The other additive reviewed in this paper is a cetane/ignition improver which has been highly applicable in low cetane indexed fuels such as alcohol additives on biodiesel to improve the ignition characteristics. Finally, the energy and exergy performance comparison of diesel and biodiesel along with different additives are also explored. Even though there is no agreement among researchers, the dominating conclusion is that the energy and exergy efficiency of biodiesel is higher than diesel fuels.